In recent years, medical treatment of the human body (e.g. electrical stimulation of various tissues or organs, delivering of medical substances into tissues or organs, and so on) has been increasingly used to treat a number of different medical conditions such as for example chronic pain disorder, alcohol and drug dependence, and other pathological conditions.
In the case of electrical stimulation, while a few of these treatments are applied by using external devices and electrodes, the majority and the most relevant of these techniques involves implanting electrodes and often the entire stimulating device in the human body.
Several commercial implantable devices have been manufactured and successfully applied and they are becoming increasingly adopted.
A typical electronic medical system for electrical stimulation includes an implantable medical device having one or more electrodes delivering electrical stimulus to a specific tissue or organ in the form of an electrical current or voltage signals.
Furthermore, the implantable medical device includes a control unit that is configured to modulate and provide an appropriate sequence of stimuli (typically, a periodic sequence of electrical voltage or current impulses), wherein the frequency, duty cycle and amplitude of the electrical signal can be adaptively varied in order to maximize the effectiveness of the treatment for each individual patient.
In addition, the implantable medical device typically includes a conductive element (e.g. a catheter) connecting the control unit to the electrodes, and an energy storage element providing the power supply to the control unit, usually in the form of an electro-chemical storage device, or a battery.
The electronic medical system having said implantable medical device has several limitations.
First of all, the control unit and energy storage element (battery) are usually integrated and occupy a relatively sizeable volume. Furthermore, both the control unit and the battery need to be suitably protected by inserting them into a rigid metallic case coated in biocompatible materials, and then implanted in a suitable anatomical cavity, in most cases disposed relatively far away from the tissue or the organ to be medically treated (e.g. electrically stimulated).
For this reason, a routing of a relatively long catheter from the control unit to the electrodes, thus increasing post-surgery patient discomfort and the probability of infections, is needed.
Moreover, the implantation of the medical treatment system typically requires at least two different surgeries on the patient.
In a first surgery, the electrodes are accurately placed in the target position (tissue or organ) into the human body, while the control unit and the battery are kept external and are connected to one another through a catheter. This is required to test the patient's reaction to the medical treatment procedure and eventually to adjust, to optimize and to fine tune the parameters of the electrical stimulus. Once the effectiveness of the medical treatment procedure has been tested, a second surgery is performed on the patient to implant the control unit in the target location. Obviously, performing two subsequent surgeries represents a inconvenience for the patient.
Furthermore, a number of disadvantages arise from the presence of an electrochemical energy storage element (battery), e.g. the limited battery's lifetime which implies the need of its replacement by surgery, the impossibility of performing Magnetic Resonant Imaging (MRI) test, the presence of heavy metals and other potentially hazardous material, such as mercury, cadmium, nickel, and lithium, requiring extra care for disposal avoiding leakage.